Spectral transmission of the He triplet at mid transit. Data points and their respective error bars are shown in black (adapted from Alonso-Floriano et al. 2019). The orange dash curve is the best fit obtained for a temperature of 6000 K, a mass-loss rate (Ṁ) of 1.9 × 10⁹ g s⁻¹, and an H/He mole-fraction ratio of 90/10 (see Sect. 4). We note that these values have changed with respect to those reported in Alonso-Floriano et al. (2019). The magenta line is a modelled absorption of the helium triplet moving along the observer’s line of sight with −13 km s⁻¹ with respect to the rest-frame of the planet and using the appropriate He(2³S) density to fit the measured spectrum. The cyan curve is the total modelled absorption. The positions of the three helium lines are marked by vertical dotted lines.